What are region locked drives?
The DVD Consortium has decided that by the year 2000 all sold DVD Drives should come region locked in hardware. This means that when you insert a region-specific disc into the drive, the drive itself checks wether the Disc's region matches the region currently set within the drive itself!
This is done completely within the drive, there is no way for a software based region selector such as DVD Genie or Remote Selector to bypass this internal region check.
As long as your drive is locked in this manor, you will be allowed upto 4 changes before the drive will be permanently locked in the last selected region. The only way to remove this locking mechanism is to replace the drive's internal control software (Firmware).
For more information see "What is a firmware".